This invention relates to bus system suitable for use in a microcomputer.
In microcomputers it is known to provide a number of functional units which communicate with one another by means of an internal bus, which is dedicated to that functional block of the microcomputer containing those functional units, and which is not directly accessible from the main data bus of the microcomputer. Different functional blocks of the microcomputer may have their own functional units and respective internal buses.
The functional units may be divided into two functional categories namely "drivers" which supply data to the internal bus and "receivers" which receive and respond to the data driven onto the internal bus by the drivers.
A problem rises in such system in respect of testing the function of the units. This is because the drivers and receivers are all tied together by the internal bus, which itself is not accessible from the main bus. Thus it is not possible to test the drivers independently of the receivers and vice-versa.
This problem is exacerbated in modular structures in which driver and receivers may be selected from a library of units and which provide many different permutations of drivers and receivers to customers requirements. This would necessitate the writing of a test sequence for each different possible combination of drivers and receivers.